Damper for regulating the flow of a gaseous medium



y 9, 1963 B. LARKFELDT ET AL 3,391,756

DAMPER FOR REGULATING THE FLOW OF A GASEOUS MEDIUM Filed Sept. 25, 1967FIGI.

INVENTORSI emszn LA RKFELDT BY JOEL ROSENBERG ATTYS.

United States Patent 3,391,756 DAMPER FOR REGULATING THE FLOW OF AGASEOUS MEDIUM Birger Larktelrlt, Odensjo, Barnarp, and Joel Rosenberg,Jonkoping, Sweden, assignors to Aktiebolaget Svenska Flaktfahriken,Stockholm, Sweden Continuation-impart of application Ser. No. 582,793,Sept. 20, 1966. This application Sept. 25, 1967, Ser. No. 670,156

2 Claims. (Cl. 181-50) ABSTRACT OF THE DISCLOSURE A damper forregulating the gaseous flow in an air conditioning or ventilating ductcomprising a regulating damper disk rotatably mounted in the duct. Thesound generated by the damper is minimized by usingperforated sheetmetal material. The hole diameters of the perforations are within therange of 1.5 and 5.0 mm., and the sum of the areas of the holes iswithin the range of and 60% of the total area of the damper.

This is a continuation-in-part of application Ser. No. 582,793 filedSept. 20, 1966 and now abandoned.

The present invention relates to a damper for regulating the flow of agaseous medium through an air conditioning or ventilating duct, whichdamper consists of a disk having the same outline as the cross sectionas said duct and mounted for turning movement therein to regulate theflow of gas therethrough.

Prior to the present invention, dampers of this type have beenmanufactured as solid dampers of sheet metal plate and have beenprovided with a coating of fabric to eliminate the noise generated bythe gaseous flow past the regulating damper. Also, circular dampers ofcloth having a rigid ring fastened thereto by sewing along theperiphery, and provided with a single hole in the center have been used.In all cases, the level of sound generated by the gaseous fiow past theregulating damper has been high, and repeated experiments have been madeto decrease further the sound level.

With a damper according to the present invention, a low sound level isobtained in a simple and effective manner which has never before beenpossible to obtain with known dampers.

A damper according to the present invention is characterized by theprovision of a rotatably mounted disk conforming in outline to the crosssection of the duct and which is perforated. The diameters of the holesforming the perforations are within the limits of 1.5 to 5.0 mm.,

and the relationship between the sum of the areas of the to theaccompanying drawing showing an exemplifying embodiment of theinvention, wherein:

FIG. 1 is a diagrammatic view of a ventilating system having a circularduct provided with a regulating damper according to the invention;

FIG. 2 is an enlarged transverse section through said duct taken on theline 22 of FIG. 1, and

FIG. 3 is a further enlarged section taken on the line 33 of FIG. 2.

In the drawing, a ventilating system is shown in FIG. 1 including aconditioner 6, a ventilating opening 7 into a room 8, and circular duct1 in which there is mounted a regulating damper 2 rotatably journalledin the duct by means of a stub shaft 3 to regulate the flow indicated3,391,755 Patented July 9, 1968 in FIGS. 1 and 3 by the arrow A from theconditioner to the opening. The damper disk according to the inventioncomprises a perforated material characterized by a plurality of holes orperforations 4 distributed over the whole damper surface and having adiameter within the limits of 1.5 to 5.0 mm. The relationship betweenthe sum of the areas of the different holes and the total area of thedamper is within the limits of 15 to 60%.

If a regulating damper in an air conditioning or ventilation plant has asolid damper disk, an under-pressure area will appear behind said damperdisk, in which area discontinuances occur, which results in disturbingsounds. This can be avoided, if, according to the invention, the damperdisk is provided with a number of holes of the size and to the extentmentioned above. In this way, the under-pressure area will, to a certainextent, be filled with air from the holes in the damper disk and will bereduced so that no disturbing sounds arise.

The limits for the hole diameter and the perforation ratio are thevalues, within which the perforation is useful in order to reduce thesound generation. Tests have shown that the sound decreases with adecreasing hole diameter to a hole diameter between 1.5 and 2.0 mm.,whereafter same increases rapidly and tends towards the value of a soliddamper disk. On the other hand, if the hole diameter is made larged than5 mm., the sound decrease is small in relation to the sound generated bya solid damper disk, and the holes may even give rise to new currentsounds. In the same way as with the hole diameter, it has been foundthat a perforation area within the range of 15 to 60% of the disk areagives a useful sound decrease.

In order to generate the lowest possible sound level, if the disk isdrilled or bored, the raw surfaces or burrs which are created whendrilling the holes in the damper disk should be turned from the aircurrent. In other words, as shown in FIG. 3, the burrs 5 of the diskshould be on the downstream side of the damper.

The invention, of course, is not limited to a certain shape or diameterof the damper disk or a certain pattern of the perforations, but thessemay be chosen freely within the scope of the invention, as defined inthe following claims.

We claim:

1. In a ventilating system having a conditioner, a ventilating openinginto a room, and duct leading to said opening, a low sound-level damperfor regulating the flow of a gaseous ventilating medium in the ducthaving a predetermined cross section comprising a single disk conformingin outline to said cross section, and means mounting said disk forrotation in said duct, said disk being perforated with holes havingdiameters within the limits of 1.5 to 5.0 mm, the relationship betweenthe sum of the areas of the different holes and the total area of thedisk being within the limits of 15 to 60%.

2. A low sound-level damper according to claim 1 wherein the holesforming the perforations impart a raw surface on one side of the disk,said one side being disposed on the downstream side of the damper.

References Cited UNITED STATES PATENTS 1,735,789 11/1929 Powell l8169 XR1,860,146 5/1932 Gray 18145 FOREIGN PATENTS 327,933 4/ 1903 France.598,629 10/1925 France. 1,044,850 6/1953 France.

ROBERT S. WARD, 111., Primary Examiner.

